Thermal compensating needle valve



April 15, 1958 D. B. PREco'rT 2,83

THERMAL COMPENSATING NEEDLEVALVE Filed June 10, 1955 FIG. 2

III-Ill INVENTOR. F 4 DAVID B. PRESCOTT ATTORNEY 2,830,621 Patented Apr.15, 1958 THERMALCOMPENSATING NEEDLE VALVE David B. Prescott, Euclid,Ohio, assignor to The Cleveland Pneumatic Tool Company, Cleveland, Ohio,a corporation of Ohio Application June 10, 1955, Serial No. 514,553 5Claims. (Cl. 13846) This invention relates generally to fluid meteringdevices and more particularly to a new and improved thermal compensatedneedle valve which automatically gompensates for changes in theviscosity of the metered uid.

It is an important object of this invention to provide a metering devicehaving new and improved means to compensate for viscosity changes of themetered fluid created by changes inthe temperature thereof.

It is another important object of this invention to provide a thermalcompensated fluid metering device which automatically adjusts theresistance to fluid flow therejtilhrrugh to compensate for changes inthe viscosity of the It is still another object of this invention toprovide a fluid metering device including an orifice with a memberprojecting therethrough wherein means are provided to automaticallyadjust the eccentricity of the member relative to the orifice tocompensate for variations in the viscosity of the fluid being metered.

Further objects and advantages will appear from the followingdescription and drawings, wherein:

Figure 1 is a perspective view of the preferred form of needle valveaccording to this invention;

Figure 2 is a side elevation partially in longitudinal section showingthe needle valve installed in the valve body;

Figure 3 is a cross section taken along 3--3 of Figure 2;

Figure 4 is a side elevation partially in longitudinal section similarto Figure 2 showing the temperature compensating action of the needlevalve structure; and

Figure 5 is a cross section taken along 55 of Figure 4.

On many occasions, a metering orifice is utilized to control the flow offluid in a device wherein it is desirable to provide a constant volumeflow for a given pressure drop even though the viscosity of the liquidbeing metered may change due to changes in the temperature thereof. Suchis the case in shock absorbers and other forms of damping mechanismswherein the resistance to movement of the shock absorber would vary withthe temperature of the damping liquid unless means have been provided toautomatically compensate for the changes in viscosity of the liquid. 1

In a metering device according to this invention, an orifice is providedinto which a needle valve projects to control the resistance of flow ofliquid through the orifice. The capacity of a given orifice with ametering member projecting therethrough varies depending upon theconcentricity of the metering member. As the metering member approachesa concentric relationship with the orifice, the resistance to flowincreases and as the metering member moves to an eccentric positionrelative to the orifice, the flow resistance decreases even though thecross section remains constant. The resistance to flow, if the flow isof the laminar or viscous type, is inversely proportional to the squareof the eccentricity of the metering member and the resistance to flowfor a given orifice with a given metering member is two and one-halftimes as great when the metering member is concentric with the orificeas resistance to flow is when the metering member is against one side ofthe metering orifice.

With this brief background, reference should be made to the drawings fora clear understanding of the metering device according to thisinvention. In Figure l, a preferred needle valve 10, according to thisinvention, is

shown. The needle valve 10 is provided with a threaded mounting portion11 adjacent to one end and a conical needle portion 12 at the other endspaced from the mounting portion 11 by a stem portion 13. The stemportion 13 is provided with a transverse groove 14 on one side of thestem axis which provides axially spaced radial walls 16 and 17.Positioned within the transverse groove 14 is a semicircular insert 18which tightly fits against the radial walls 16 and 17. The needle valve10 and the insert 18 are formed of dissimilar metals having differentcoeflicients of expansion.

Referring to Figure 2, the needle valve 10 is shown as it would beinstalled in a valve body 19 which is provided with a first bore 21adapted to loosely receive the stem 13 of the needle valve 10 andterminating in a coaxial r conical portion 22. The valve body 19 is alsoprovided with an inlet passage 23 opening into the bore 21 and an outletpassage '24 in communication with the small end of the conical portion22. The mounting portion 11 is threaded into the bore 21 and a resilientseal 26 prevents leakage between the needle valve and the body. A stoplug 27 is formed in the conical portion 22 and is proportioned to engagethe needle portion 12 when it is ,concentric with the bore 21. Theneedle valve is shown in Figure 2 with the needle portion 12 concentricwith the conical portion 22 which is the position assumed when thehighest resistance to flow is produced. This would be the position ofthe elements when the temperature of the liquid being metered is highand the viscosity of the liquid is low.

If the liquid cools, the viscosity increases so it is necessary to movethe needle portion 12 away from its concentric position toward theeccentric position shown in Figures 4 and 5 so that the resistance toflow of the needle valve will be reduced and a constant flow for a givenpressure differential will be maintained. Since the stem portion issurrounded by the metered liquid, the stem 13 and insert 18 will be atthe same temperature as the liquid. By choosing a metal for the insert18 with a coefficient of expansion less than the coefficient ofexpansion of the metal used to form the needle valve 10, it is possibleto achieve an automatic deflection of the needle portion 12 toward theeccentric position as the temperature decreases. If the parts arearranged so that the stem portion 13 is straight when the needle valveis at a temperature at the high side of the compensated temperaturerange, cooling will create a shrinkage of the metal of the stem 13 whichis greater than the shrinkage of the metal of the insert 18 for a givenamount of cooling. This will cause an increased pressure'bet'ween theinsert 18 and the radial walls 16 and 17 which willcause the stemportion 13 to bend (as's'hown in Figure 4). This moves the needleportion 12 from the concentric position toward the eccentric positionwith the amount of eccentricity a function of the amount of cooling.

By properly choosing the proportions and the materials utilized to formthe insert 18 and the stem portion 13 for a given liquid, it is possibleto produce a compensated metering device which will allow essentiallyconstant volume flow for a given pressure drop through relatively widevariations in temperature. Because there are no sliding parts or wearingsurfaces in a metering device according to this invention, the devicerequires essen- 3 4- tially no maintenance or inspection and will give along portion being formed with a transverse groove providingtrouble-free service life. 7 axially spaced radial walls, and"an insertelement in said In the above detailed description and in the drawingsgroove engaging said radial walls formed of a material showmmyjnventionis applied toa, needle valve used to having a coeflicient of expansiondifierent than the cothechanges in viseosigl. However, other forms 5efficient of expansion of said stern whereby said metering of, meteringdevices pnovided with a metering orifice and portion approachedconcentricity with said orifice as the e er n 52 31)?! projecting ththrough may be utilized stem and element reach a predeterminedtemperature and for use in all applications where temperaturecompensamove away from said concentric position as said tempertiondesired to or change a flow rate. r ature decreases.

Although a preferredembodiment of this invention is 1.) 4. A thermalcompensating fluid metering device comillustr'ated it be realized thatvarious modifications prising a housing formed with inlet and outletpassages of the strnctln'al details-may be made-without departingconnected by a metering orifice, a valvemember mounted from the mode ofoperation and-the-essence of the inin said housing at a point spacedfrom said orifice formed eu io Th refore, xcfin inso ar 'as1hey areclaime with a stem portion having a coefficient of expansion and in theappended claims, structural details may be varied F a metering portionextending into said orifice, said stem widely without modifying the modeof operation. Acportion being formed with a transverse groove on onecordingly, the appended claims and not the aforesaid side of the axisthereof providing axially spacedradial d t 2 1,lltl d 8l'jpti0fl,3i' 6determinative of the scope of the walls, and an inscrtelement. in saidgroove engaging said invention. radial walls formed of a material havinga coeflicient of I cljai rn; expansion smaller than the coefiicient ofexpansion of 1, A thermalcompensating fluid metering device comsaid stemwhereby said metering portion approachescom prising a housing formedwith inlet and outlet passages ceniricity with said orifice as the fluidreaches a predeterconnected by a conical metering orifice, a valvemember mined temperatureandmoves away from said concentric mountedinsaidhousing formed with a conical metering position as saidtemperature decreases. portionextending into said orifice, the mountingof said 25 S. A thermal compensating fluid metering device comvalvemember positioning said metering portion concenprising a housing formedwith inletand .outlet passages trio with said orifice when the fluid isat one temperature, connected by a meteringorifice, a valve membermounted astop lug in said orifice engaged by said metering porin saidhousing at a point spaced from said orifice formed tion when; in saidconcentric position, and means autowith a stem portion havingacoeflicient of'expansion and rnatically moving said metering portionlaterally away 30 a metering portion extendingjnto said orifice,vsaidstem from"sai d concentric position upon fluid temperature portion beingformed with a transverse groove on one i fchangestromsaidfinetemperature. side of the axis thereof, providingaxially. spaced-radial 2. A theijmal compensating fluid metering devicecomwalls, an insert element, in, said; groove, engaging said prising,ahousing.formed withinlet and outlet passages radial walls forme'dof'amaterialhaving a,coefiicient of -connectedby ametering' orifice, avalve member mounted 3: expansion smaller than jthe, coeflicient. ofexpansion of in saidhousingat apoint spaced from said orifice formedsaid stem whereby saidjmeteringportion approaches conwith a, meteringportion extending into said orifice, an centricity with said orificeasthe, fluidreaches apredesaidlvalv'e formedof a material having atermined temperature and moves away. fromsaid conco-eflicient ofiexpansindifierent from that of said valve centric position as said temperaturedecreases, and stop whereby said metering portion approachesconcentricity 40 means limitinglateralgmotion ofsaid metering portion.withsaid orifice as the fluid reaches a predetermined temin onedirection when said orificeand metering portion are perature and moveslaterally away from said concentric concentric.

position assaid temperature changes.

3. 'A thermal compensating fluid metering device com- References Citedin the file of this patent prisinga housing formed with inlet and outletpassages 5;-

connected by a metering orifice, a valve member mounted UNITED STATESPATENTS in said housingat a point spaced from said orifice formed1,922,266 Toman Aug. 15, 1933 with a-stem portion having a coefl'icientof expansion and 2,582,324 Gailloud Jan. 15, 1952 a metering portionextending into said orifice, said stem

